Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a first image in a sequence for a display screen or portion thereof with transitional graphical user interface showing our new design;

FIG. 2 is a second image thereof;

FIG. 3 is a third image thereof;

FIG. 4 is a fourth image thereof;

FIG. 5 is a fifth image thereof; and,

FIG. 6 is a sixth image thereof.

The appearance of the animated user interface sequentially transitions between the images shown in FIGS. 1-6. The process or period in which one image transitions to another forms no part of the claimed design. The broken lines show a display screen or portion thereof and the portions of the graphical user interface which form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 